Phase change mass transfer model for frost growth and densification

摘要

A frosting mechanism was used to develop a phase change mass transfer model to predict the frost layer growth and densification. The model with a criterion can describe the mass transfer of water vapor from the humid air to increase the frost thickness and the frost density. Frost formation on a cold surface with local cooling was simulated by using the model as a source term in FLUENT to predict the frost morphology, temperature distribution and frost weight which are all in good agreement with the experimental results. The results show that the frost first forms around the cooling block and then extends gradually to other directions, with the frost above the cooling block having the greatest density. The average frost thickness increases gradually with time with the growth rate slowing down, while the average frost density increases with the increases rate getting faster. The temperature distribution in the computational domain is related to the frost layer morphology and the frost surface temperature is usually lower than the freezing point temperature. As the frost layer grows, the average air velocity increases with the maximum local velocity located above the thickest part of the frost layer.